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Sowing larger patches of flowers can increase bumblebee reproduction in areas surrounding intensive arable farms

Science for Environment Policy  │  Thematic Issue 57  │   June 2017

Agri-environment schemes (AES) have been implemented throughout Europe to mitigate against the negative effects of agricultural intensification. Although these schemes have shown positive effects on the

abundance and richness of certain species and taxa, the impact of AES on reproduction of target species at the local and landscape scale is poorly understood. This large-scale study looked for the effect of selected AE measures on bumblebee reproduction. Results indicate that bumblebee reproduction is significantly higher on sown flower patches when compared to conventional management. Although the increase is most pronounced at the plot scale, higher reproduction was found in landscapes surrounding larger sown plots (at least one hectare) compared to smaller sown plots.

Agricultural intensification can result in the loss and fragmentation of habitats, leading in some cases to species decline. To mitigate these declines, the EU has established agri-environment schemes (AES), which compensate farmers for undertaking practices beneficial for biodiversity, such as maintaining existing habitats or creating new habitats.

These practices have been shown to benefit a range of birds, bees and plants by increasing the number of individuals and species, but there is debate as to whether this translates into long-term benefits for biodiversity. In particular, there is limited evidence that AES have positive effects on reproduction of certain taxa (and thus the persistence of populations).

Contributing to the evidence base, this study focused on several species of bumblebees (Bombus), which play an important role as agricultural pollinators, but are now of high conservation concern due to the widespread declines in populations over recent years. The study focused on the importance of flower-rich habitats for bumblebees, more specifically, on the effect of newly sown flower mixtures on bumblebee reproduction (i.e. the abundance of males and queens, i.e. sexuals).

The researchers conducted a large-scale study across seven sites in England, with varying levels of agricultural intensity. At each site, a flower mixture (20% legume and 80% fineleaved grasses — as recommended under the AES ‘nectar flower mixture’ option under the Entry Level Stewardship (ELS) scheme in England), was sown in patches of various sizes (0.25–1ha).

The patches were established on land taken out of arable production. Control ‘patches’ were selected at each of the seven sites to represent non-crop vegetation that was typical of the area, i.e. the non-crop vegetation that would normally be available to bees in the absence of a sown flower patch or margin. Control patches were always within around 3km distance of sown patches — so that all four patches at a site were separated by an average of 3km…

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SOURCE: EC – Science for Environment Policy